There’s no shortage of large sensors, they just don’t make sense in a phone unless you want it to be huge. In fact there’s a migration upwards in camera sensor sizes owing to the decreasing size of the support electronics, e.g. you can now get a Hasselblad medium format camera that’s smaller than a DSLR. Of course the lenses are huge.

I for one would love for Apple or Samsung or whoever to release a photographer’s smartphone with a micro 4/3 mount (it’s the only multi firm properly documented lens mount system and also seems to be the sweet spot for trading off image quality, sensor readout speed, and size) BUT the phone would be at minimum 20mm thick.

No shortage? Are you kidding? There is only Sony and Canon who make full frame sensors right now at mass market level (nikon is supplied by Sony), and the amount of cameras available with not-really-medium-format size, you can count on one hand. This is a far cry from the situation of film cameras where you had at least at least several dozens of medium format cameras available for purchase at once.

Are you talking about sensors or film? Kodak and Fuji dominated film, and today Sony and Canon dominate sensors (Samsung had a pretty solid go of it and simply gave up). Lots of other companies make sensors but they aren’t competitive with Sony.

There are plenty of camera companies, mostly using Sony sensors or Sony fabs.

The lack of manufacturing diversity isn’t a shortage. It’s a different problem. Is there a shortage of cpus?

What about CMOSIS, well, to be fair, the CMV50000 is still just sampling without bayer, but it's a really nice sensor, and you can't really say that it's brother the CMV12000 is bad.